If your character is a caster that has a high level of intelligence than this fight shouldn't be too difficult. Focus on using whichever version of Homing Soulmass you have and cast the various fire spells your character has available.

If you are a faith user this will be especially difficult. Most faith spells are lightning based and are almost completely useless against the Sanctuary Guardian. Your best bet is to be in human form and try to summon help. If you can't find help, earn the Rite of Kindling so you can heal more because you are going to have to get up close and personal.

Faith users will need Wrath of the Gods, Karmic Justice and Replishment to make this fight easier. Use Wrath of the Gods up close for some quick hard hitting damage. Cast Karmic Justice and Replishment when all of your range spells are depleted. Karmic Justice will unleash damage as the Sacred Guardian is pummeling you. Replishment slowly heals you and recovers your stamina quicker.

Melee fighting the Sanctuary Guardian isn't as hard as it may seem. Be as light as possible coming in to the fight. Dodging is your main defensive option so heavy armor is a no go for this fight. Ideally your equipment load will be below 25% so that your character can dodge the maximum distance. Your weapon should be something quick, or something with reach. In the video you will see the player using a Scimitar wielded with both hands. A long Polearm style weapon would also work.

There will be two specific attacks that a melee character can capitalize on. The first is where he lifts himself up on his hind legs and drogs, sending out a tremor towards you. This is easy to spot and dodge, allowing you to run up and land a few quick hits. The second is where he jumps straight towards you for a headbut. Roll straight back and you will end up nearly side by side with the beast. This sets you up wonderfully and you will be able to land multiple blows. Three hits should be enough with most weapons to cause him to stagger. Remeber to use caution when meleeing. Don't get greedy, ever. It takes only one slip for him to pounce and destroy you. Only swing when you are sure there is an opening to take advantage of.

Occasionally the guardian will fly around. When he does watch out for lightning attacks above. He usually misses, but be cautious. The lightning attacks from above do AoE damage, so even if he misses dodge to the side a couple times to remove yourself from the area.

After defeating the Sacred Guardian you can continue on into the Oolacile Garden.

If you were unable to cut the guardian's tail off don't worry. Upon returning to this area you will now face two Sanctuary Guardians, both of which can yield the unique item.